Put the dates, almond butter and vanilla extract in a food processor or blender. Pulse until fully blended; the date mixture should be paste-like.
Roll the date mixture into about 16 little balls.
Stick a toothpick in each date ball (a handle for dipping later.)
Put the date balls in the freezer for about 30 minutes, until they become firm.
Meanwhile, heat 4 ounces of chocolate in a double boiler. If you haven't got a double boiler, fill a saucepan with a few inches of water and lay a heatproof bowl on top of it. Bring the water to a boil; melt the chocolate in the heatproof bowl on top.
When the chocolate is about 80% melted, stir in ½ teaspoon of canola oil to thin the chocolate out for easy dipping.
Using the toothpicks as handles, dip each date ball in the chocolate. Swirl to coat well. Transfer each chocolate-dipped date ball to a sheet of waxed paper.
Allow the date balls to sit out at room temperature for 1 hour to cool (they will cool faster in the refrigerator.)